Conventional high-frequency heating apparatuses are a microwave oven having a high-frequency generator for heating, and a combination oven to which a convection heater for generating hot air in this microwave oven is added. Further, a steamer for heating an object by introducing steam into a heating chamber, and a steam convection oven, in which a convection heater is added to a steamer, are utilized as cooking apparatuses.
When food is cooked by the cooking apparatus, the cooking apparatus is controlled to make the finished state of the food the best condition. That is, cooking performed by combining a high-frequency heating technique with a hot-air heating technique, and cooking performed by combining a steam heating technique with a hot-air heating technique are controlled by the steam convection oven. However, the cooking performed by combining the high-frequency heating technique and the steam heating technique troubles a user to transfer the heated food between separate cooking apparatus each used for heat-treating according to a corresponding one of these techniques. There has been developed a cooking apparatus enabled to achieve by itself high-frequency heating, steam heating, and electric heating so as to resolve such inconvenience. This conventional cooking apparatus is disclosed in, for example, JP-A-54-115448.
However, according to the configuration of the conventional cooking apparatus disclosed in JP-A-54-115448, a vaporizing chamber for generating heating steam is embedded in a lower portion of the heating chamber, and adapted to be always supplied with water from a water storage tank maintained at a constant water level. Therefore, it is difficult to perform a daily work of cleaning around the heating chamber. Especially, in the vaporizing chamber, during the process of generating steam, calcium and magnesium contained in water content are condensed, deposited and fixed onto the bottom portion of the vaporizing chamber and in a pipe to thereby reduce an amount of generated steam. Consequently, the conventional cooking apparatus has a problem that the environment of the heating chamber is so unsanitary that the propagation of fungus easily occurs.
Further, although a method of generating steam by using a heating means, such as a boiler, disposed outside the heating chamber and supplying the steam generated therein to the heating chamber is considered as a way of introducing steam into the heating chamber, troubles, such as propagation of saprophytes, breakage due to freeze-up, and contamination by foreign material owing to rust, occur in a pipe for introducing steam. Moreover, the heating means are usually difficult to disassemble and clean. Therefore, it is difficult for a cooking apparatus, which treats food and needs a lot of attention thereto, to employ the method of externally introducing steam.
Furthermore, although it is usual that a temperature sensor, such as an infrared ray sensor, for measuring the temperature of an object to be heated is provided in a cooking apparatus, the infrared ray sensor measures the temperature of suspended steam particles, which are present between the sensor and the object, instead of the temperature of the object. Thus, the temperature of the object cannot be measured. Then, a heating control adapted to operate according to a result of detection of the temperature, which is performed by the infrared ray sensor, does not normally operate. Consequently, troubles, for instance, under heating or overheating occur. Especially, in the case of following a sequential procedure for performing automatic cooking, even when under heating occurs, control advances to the next step without compensation. Thus, the conventional cooking apparatus cannot deal with the underheating problem by simply performing reheating or radiational cooling. Consequently, the cooking may results in failure.
Further, the conventional cooking apparatus has another problem that this apparatus cannot necessarily heat the object by using a heating pattern, which has high heating efficiency, according to the kind of the object and to the temperature conditions thereof in the case where the object is a frozen food or a chilled food, and that thus, along heating time is necessary.